JP3814858B2 - In-cylinder direct injection internal combustion engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine such as an automobile, and more particularly to a control device for a direct injection type internal combustion engine having a direct injection injector that directly injects fuel into a cylinder at a high pressure.
[0002]
[Prior art]
In a direct injection type internal combustion engine, it is desirable to supply the fuel after the fuel pressure (hereinafter referred to as fuel pressure) becomes high in consideration of atomization of the fuel so that the engine is surely started at the time of starting. For this reason, conventionally, high fuel pressure is generated using a mechanically driven high-pressure fuel pump in consideration of fuel efficiency and efficiency.
[0003]
However, when the engine is started, this high-pressure fuel pump becomes a load, and the increase in engine speed is delayed, and consequently the increase in fuel pressure is also delayed.Therefore, if fuel supply is made after waiting for the fuel pressure to rise sufficiently, the result is In some cases, engine start-up may be delayed. Also, if the fuel supply is made too early with the fuel pressure insufficient to speed up the start, the fuel supply amount may be insufficient depending on the operating conditions, resulting in poor combustion or misfire, leading to deterioration of exhaust and startability.
[0004]
In order to avoid such inconvenience, Japanese Patent Laid-Open No. 4-311637 discloses that in an internal combustion engine equipped with a direct injection injector, when the engine speed at the start is lower than a predetermined value, at the end of the compression stroke. Start the supply of fuel so that the injected fuel is stratified around the spark plug, and if the engine speed is higher than the predetermined value, supply the fuel when the exhaust valve closes. A technique for burning so as to form a uniform air-fuel mixture in the combustion chamber is disclosed. This is intended to realize a rapid increase in the engine speed without deteriorating exhaust and starting performance.
[0005]
[Problems to be solved by the invention]
However, in such a control apparatus for a conventional direct injection type internal combustion engine, attention is paid only to the number of revolutions at the time of starting the engine, the fuel supply amount and the state of the fuel pressure are not taken into consideration, and the starting is started. The first fuel supply is always started in a predetermined cycle.
For this reason, when the fuel supply start cycle is set early, if the fuel pressure is low, the supply amount may be insufficient, and exhaust may deteriorate due to poor combustion or misfire. If it is set late, there is a problem that it takes more time than necessary to start the engine even under good conditions where the temperature is high and the engine can be started quickly.
[0006]
In view of such conventional problems, the present invention is based on the rotational speed at the time of engine start, the amount of fuel supply, the fuel pressure increase characteristic of the fuel pump, the fuel pressure detection value, the fuel temperature detection value, etc. Accordingly, an object of the present invention is to provide a control device for a direct injection type internal combustion engine that can control the fuel supply start cycle variably and can start the fuel supply from the optimum cycle.
[0007]
[Means for Solving the Problems]
For this reason, the present invention waits for a sufficient increase in fuel pressure under conditions where it is necessary to supply a large amount of fuel at the start, such as at low temperatures, and the engine speed is low and the fuel pressure rises slowly. The basic principle is to prevent exhaust and deterioration of startability by supplying fuel. On the other hand, under conditions where only a small amount of fuel is required at start-up, such as at high temperatures, and the engine speed is high and the fuel pressure rises quickly, the engine can be started quickly by starting fuel supply at a relatively fast cycle. Is realized.
[0008]
Specifically, in the invention according to claim 1, in a control apparatus for a direct injection type internal combustion engine in which fuel is directly injected into a cylinder at a high pressure by a direct injection injector, as shown in FIG. An operation state detection means A for detecting an operation state, a fuel supply amount calculation means B for calculating a fuel supply amount at the time of starting the engine, a detection result of the operation state detection means, and a calculation result of the fuel supply amount calculation means Based on the fuel pressure lower limit calculation means C for calculating the lower limit value of the fuel pressure required at the start, the detection result of the operating state detection means, and the calculation result of the fuel supply amount calculation means A fuel pressure estimator D for estimating a change in fuel pressure when the fuel pressure is detected, a fuel supply for determining a cylinder to start fuel supply at startup based on the calculation result of the fuel pressure lower limit value calculator and the estimation result of the fuel pressure estimator Open Characterized in that it is configured to include a cylinder determining means E, a.
[0009]
  In the invention according to claim 2,The fuel pressure estimating means D preliminarily estimates a change in fuel pressure due to fuel supply before supplying fuel.
  In the invention according to claim 3,The fuel pressure estimation means D calculates the fuel pressure after fuel supply from the crank angle detected by the operating state detection means A, the fuel supply amount calculated by the fuel supply amount calculation means B, and the characteristics of the known fuel pump. It is characterized by estimating changes.
[0010]
  In the invention according to claim 4, the predetermined fuel pump characteristic is a fuel pressure increase characteristic of a fuel pump corresponding to a crank angle.
  Also,Claim 5In the invention according to claim 1, the fuel pressure estimating means includesCrank angle sensor 180 ° CA For each reference signal output every time, the transition of the fuel pressure is estimated,The fuel pressure estimated based on the previous fuel pressure estimated value with the final value of the previous fuel pressure estimated value as the initial value, and the fuel pressure decrease amount calculated based on the fuel supply time calculated from the estimated fuel pressure and the fuel supply amount, From this, it is characterized by estimating the transition of the fuel pressure.
  Also,Claim 6In the invention according toWhen estimating the initial fuel pressure after starting, the initial value is the crank angle at starting,Fuel pressure increase characteristics of pre-stored fuel pumpWhenIt is calculated | required by.
  Also,Claim 7In the present invention, the operating state detection means A detects the crank angle of the engine by a crank angle sensor installed in the internal combustion engine, and calculates the engine speed based on the crank angle sensor. And
  Also,Claim 8In the invention according to the present invention, the fuel supply amount calculation means B determines the fuel supply amount at the time of starting the engine from a predetermined table based on the coolant temperature of the engine.
  Also,Claim 9In the invention according to the above, the fuel pressure lower limit calculating means C includes a maximum time during which fuel can be calculated, which is calculated based on a crank angle section in which fuel can be supplied and an engine speed detected by the operating state detecting means, From the fuel supply amount calculated by the fuel supply amount calculation means B, a lower limit value of the fuel pressure required to finish supplying the fuel supply amount within the maximum time is calculated from a predetermined table. Features.
[0011]
  Also,Claim TenIn the invention according to the present invention, the fuel pressure lower limit value calculating means C includes a limiter for limiting the minimum value of the fuel pressure lower limit value, and includes a fuel pressure lower limit value correcting means for correcting the calculated lower limit value of the fuel pressure. Features.
[0012]
  Also,Claim 11In the invention according to the invention, the internal combustion engine includes a fuel pressure sensor that detects a fuel pressure, while the fuel pressure estimation means D is calculated by the crank angle detected by the operating state detection means A and the fuel supply amount calculation means B. A change in the fuel pressure is estimated from the fuel supply amount, the characteristics of the known fuel pump, and the output of the fuel pressure sensor.
[0013]
  Also,Claim 12In the present invention, the internal combustion engine includes a fuel temperature sensor for detecting a fuel temperature, while the fuel pressure estimating means D is calculated by the crank angle detected by the operating state detecting means A and the fuel supply amount calculating means B. The fuel pressure change is estimated from the supplied fuel amount, the characteristics of the known fuel pump, and the output of the fuel temperature sensor.
[0014]
  Also,Claim 13In the invention according to the present invention, the fuel supply start cylinder determination means E includes the estimated value of the fuel pressure after the fuel supply calculated by the fuel pressure estimation means D and the fuel pressure lower limit value calculated by the fuel pressure lower limit value calculation means C. If the estimated fuel pressure is equal to or greater than the lower limit of fuel pressure, fuel is supplied to the cylinder at which the fuel supply timing has been reached, and if the estimated fuel pressure is smaller than the lower limit of fuel pressure, fuel is supplied. It is characterized in that the cylinder which starts the fuel supply is determined by performing the same processing at the next fuel supply timing without performing the supply.
[0015]
  Also,Claim 14The invention according to the present invention is characterized in that the present control is terminated when a predetermined period elapses after the engine is started.
[0016]
【The invention's effect】
In the present invention, using the engine speed, the fuel supply amount, the fuel pressure increase characteristic due to the characteristics of the fuel pump, the fuel pressure detection value, the fuel temperature detection value, etc. The cycle is variably controlled. As a result, when it is necessary to supply a large amount of fuel at start-up, such as at low temperatures, and when the engine speed is low and the fuel pressure rises slowly, the fuel supply must be waited for the fuel pressure to rise sufficiently. By doing so, there is an effect that deterioration of exhaust can be prevented. Also, under conditions where only a small amount of fuel is required at start-up, such as at high temperatures, and where the engine speed is high and the fuel pressure rises quickly, fuel supply is started at a relatively fast cycle to achieve quick engine start-up. As a result, it is possible to prevent the deterioration of exhaust and the startability due to the deterioration of combustion or misfire.
[0017]
  That is, according to the first and second aspects of the present invention, it is possible to determine the fuel supply start timing at start-up in the direct injection type internal combustion engine, and to prevent deterioration of combustion, exhaust deterioration due to misfire, and start-up delay. There is an effect.
  Moreover, Claim 3Claim 6According to the present invention, since the change in the fuel pressure is estimated from the characteristics of the fuel pump known in advance, there is an effect that the fuel pressure can be estimated easily and accurately.
  Also,Claim 7According to the present invention, it is possible to easily and accurately detect the operating state of the engine, and it is possible to perform accurate control based on this.
[0018]
  Also,Claim 8According to the present invention, there is an effect that the fuel supply amount at the start can be easily calculated.
  Also,Claim 9According to the invention, since the optimum fuel pressure lower limit value is calculated based on the fuel supply amount and the engine speed, even when the fuel supply amount and the engine speed at the start are different, exhaust and startability are deteriorated. There is an effect that can be prevented.
[0019]
  Also,Claim TenAccording to the invention, the correction is performed by limiting the minimum value of the fuel pressure lower limit value, so that even when the fuel supply amount is small and the engine speed is slow, the atomization of the fuel becomes insufficient. As a result, the exhaust and startability can be prevented from deteriorating.
[0020]
  Also,Claim 11According to the invention, the fuel pressure is estimated more accurately by using the output value of the fuel pressure sensor to estimate the change in the fuel pressure when the fuel is supplied to the cylinder where the fuel supply timing comes next time. There is an effect that can be.
  Also,Claim 12According to the present invention, there is an effect that the fuel pressure can be accurately estimated even when the fuel property changes due to the difference in the fuel temperature and the fuel pressure increase characteristic of the fuel pump changes.
[0021]
  Also,Claim 13According to the invention, there is an effect that fuel supply can be performed well and reliably by preventing the fuel pressure after fuel supply from falling below the fuel pressure lower limit value.
  Also,Claim 14According to the present invention, since the execution of this control is limited to a predetermined period after the start, there is an effect that it is possible to prevent the fuel supply from being accidentally stopped during the normal operation after the start. is there.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a cross-sectional view of a direct injection internal combustion engine showing an embodiment of the present invention. In the engine 1, intake is performed through the throttle valve 2, the surge tank 3, the intake manifold 4, and the intake valve 5, and fuel is directly injected from the direct injection injector 6 into the combustion chamber 7. The spark plug 8 is provided with an electrode for ignition facing the combustion chamber 7.
[0023]
As means for detecting the operating state of the engine 1, an air flow meter 9 provided upstream of the throttle valve 2 for measuring the intake air amount, a crank angle sensor (not shown) for measuring the crank angle position of the engine 1, Etc. are provided. The crank angle sensor is directly or indirectly connected to the crankshaft or a camshaft that rotates in conjunction with the crankshaft, and calculates the crank angle position (crank angle) and the rotational speed of the engine 1.
[0024]
Further, a fuel pressure sensor 10 for detecting the fuel pressure of the supplied fuel is provided, and the air-fuel ratio is controlled by adjusting the fuel injection amount by the direct injection injector 6. In addition to this, a water temperature sensor 11 that measures the engine coolant temperature and an O that measures the oxygen concentration in the exhaust gas.₂A sensor 12 and the like are provided.
Input / output of information with the outside and various operations are realized by a circuit centered on the microcomputer shown in FIG. Various sensors such as the above-described air flow meter 9 are connected to the input port 13, and information thereof is input. The A / D converter 14 performs A / D conversion so that an analog signal among signals obtained from various sensors via the input port 13 can be handled by a computer. The CPU 15 executes a predetermined calculation based on the input data, and the result is output from the output port 16 as a signal for driving and controlling an external device.
[0025]
The ROM 17 stores a control program and various data described later in advance, and the RAM 18 temporarily stores information during program execution.
In the above-described conventional direct injection type internal combustion engine, the fuel supply amount at the start is determined based on the water temperature or the like, but the cycle for starting the fuel supply is generally fixed. In addition, in a direct injection type internal combustion engine, it is necessary to increase the pressure of the fuel in order to atomize and supply the fuel in a short time, and a mechanical high pressure fuel that is driven by a camshaft or the like in consideration of fuel efficiency and efficiency. A pump is used.
[0026]
Therefore, in order to start the engine by supplying fuel, it is first necessary for the pump to discharge high-pressure fuel. In addition, in order for the pump to rotate and discharge high-pressure fuel, the engine must be rotating at a predetermined speed.
Here, when the engine speed at the start is low due to a low battery voltage, etc., and when a large amount of fuel must be supplied because the temperature is low, a large amount of fuel is supplied at a low fuel pressure. Since it tries to supply, as a result, a fuel pressure falls further and supply amount and atomization of fuel become inadequate. As a result, combustion at the time of start-up deteriorates, and in the worst case, misfire occurs, leading to deterioration of exhaust and startability.
[0027]
Now, let us consider a case in which fuel injection is performed in the intake stroke at the time of starting in a direct injection type internal combustion engine. In general, the opening and closing timings of the intake valve and the exhaust valve are set as shown in FIG.
Here, the exhaust valve is open at the initial stage of the intake stroke, and if the fuel is supplied, the fuel may be exhausted as it is, so that the fuel cannot be supplied. Also, in the first half of the intake stroke, the piston is not lowered so much, and if fuel is supplied, the fuel may adhere to the piston, resulting in insufficient atomization and deterioration of exhaust. On the other hand, if fuel is supplied immediately before the intake valve is closed, the piston starts to rise, and the air-fuel mixture may be pushed back to the intake port side. Therefore, it is desirable to select a range such as the “fuel supply available section” in FIG.
[0028]
Generally, the fuel supply amount is determined by the product of the differential pressure between the fuel supply atmospheric pressure (in this case, the cylinder pressure) and the fuel pressure and the fuel supply time. Here, since the in-cylinder pressure at the time of starting is substantially atmospheric pressure, when the fuel supply amount Ti is constant, the relationship between the fuel pressure Pfuel and the fuel supply time Tpulse is as shown in FIG. Further, the upper limit value T1 of the fuel supply time can be calculated from the engine speed N at that time and the fuel supply available section of FIG. 4, and if the fuel supply amount is Ti1, then the relationship shown in FIG. The lower limit value P1 of the fuel pressure necessary for supplying the fuel supply amount Ti1 to the fuel is obtained.
[0029]
Even if the engine speed N is low and the fuel supply time can be extended, the fuel pressure is not necessarily low, and there is a minimum fuel pressure required to atomize the supplied fuel. Therefore, when considering this, it is necessary to further correct the fuel pressure lower limit value obtained from FIG. Alternatively, as shown in FIG. 5, a lower limiter for the fuel pressure lower limit value may be provided in advance.
[0030]
FIG. 6 shows the fuel pressure increase characteristic at the time of start by the fuel pump when the fuel supply to the cylinder is not performed, and the fuel pressure increases smoothly with the passage of time. However, in actuality, when fuel is supplied, the fuel pressure is lowered. When the fuel pressure is lower than the above-described fuel pressure lower limit P1, the fuel supply amount becomes insufficient.
In the following, an example will be described in which a four-cylinder direct injection internal combustion engine is used in which the fuel pump discharges four times per two engine revolutions. In all cases, the state of the battery, the cranking rotation speed at start-up, and the upper limit value T1 of the fuel supply time are the same. Further, referring to FIG. 5, the fuel supply amount at high temperature is Ti1 (fuel pressure lower limit is P1), and the fuel supply amount at low temperature is Ti2 (fuel pressure lower limit is P2). Despite direct injection, the amount of fuel supplied at start-up differs depending on the temperature.For example, at low temperatures, the amount of fuel supplied is scraped off from the cylinder to the crankcase. This is because, while it has to be supplied, there is almost no fuel scraped off into the crankcase at high temperatures, so only the amount necessary for combustion needs to be supplied. Another reason is that the amount of fuel required differs because the air density varies with temperature.
[0031]
In the case of Ti1 where the fuel supply amount is relatively small at high temperature, even if the fuel injection pulse is output from the cylinder (# 1 cylinder) that first takes the intake stroke as shown in FIG. 7, the fuel pressure Pfuel decreases so much. In addition, even before the first explosion of cylinder # 1, the fuel pressure lower limit value P1 is not fallen, and the fuel supply to the subsequent cylinders (# 3) is smoothly performed. Reach the speed.
[0032]
On the other hand, in the case of Ti2 at a low temperature and a relatively large amount of fuel supply, as shown in FIG. 8, when fuel is supplied to the cylinder (# 1 cylinder) that first takes the intake stroke, the fuel pressure decreases and the fuel pressure There are cases where the fuel supply amount of each cylinder (# 3, # 4 cylinder) until the first explosion of the # 1 cylinder falls below the lower limit value P2 is insufficient. As a result, even if the first explosion occurs, the fuel supply amount of those cylinders (# 1, # 3, # 4 cylinders) is insufficient, so the combustion deteriorates, the increase in the rotational speed is slow, and the startability deteriorates. At the same time, the exhaust also gets worse.
[0033]
However, in such a case, before supplying fuel to the # 1 cylinder, the fuel pressure change due to the fuel supply is estimated in advance from the characteristics of the high-pressure fuel pump, the output of the fuel pressure sensor, the output of the fuel temperature sensor, etc. Can be avoided. That is, as shown in FIG. 9, when it is estimated that the fuel pressure is lower than the lower limit P2 of fuel pressure, the fuel pressure is not supplied to the # 1 cylinder but the fuel pressure is increased. Then, before the next supply to the # 3 cylinder, it is determined again whether or not the fuel can be supplied. If it is determined that the fuel pressure does not fall below the fuel pressure lower limit P2 even if the fuel is supplied to the # 3 cylinder, the fuel is supplied from the # 3 cylinder. To start. In this way, deterioration of combustion or exhaust deterioration due to misfire can be prevented, and as a result, the target rotational speed is reached more quickly than when fuel is supplied from the first cylinder at a low fuel pressure. It is also possible.
[0034]
A first embodiment for performing such processing will be described below.
FIG. 10 shows a routine for detecting the driving state, which corresponds to the driving state detecting means A. Here, it is executed at regular intervals (10 ms), but may be executed at different timings such as a background job.
In step 1001 (shown as S1001 in the figure, the same applies hereinafter), the output of the crank angle sensor is read. In step 1002, the current crank angle is detected from the data read in step 1001. In step 1003, the engine speed N rpm is calculated from the data read in step 1001, and this routine is terminated.
[0035]
FIG. 11 is a routine for calculating the fuel supply amount and corresponds to the fuel supply amount calculation means B. This is executed in synchronization with a reference signal output every 180 CA ° from the crank angle sensor.
In step 1101, the water temperature Tw is read from the water temperature sensor 11, and in step 1102, the value of the starting fuel supply amount Ti corresponding to the current water temperature Tw read in the previous stage is read from a table as shown in FIG. If the water temperature is Tw1, the fuel supply amount is Ti1), and this routine is terminated.
[0036]
FIG. 12 is a routine for calculating the lower limit value of the fuel pressure, and is executed for each reference signal. This corresponds to the fuel pressure lower limit calculation means C.
In step 1201, the predetermined fuel supply available section Cpulse ° CA shown in FIG. 4 is read, and in step 1202, the rotational speed N calculated in step 1003 of FIG. 10 is read. In step 1203, the upper limit value T1 of the fuel supply time is calculated from the read Cpulse and N by the following equation.
[0037]
T1 = Cpulse x 1000 / (6 x N) ms
In the following step 1204, the fuel pressure lower limit value P is calculated from the table shown in FIG. 5 based on T1 calculated in step 1203 and the fuel supply amount read in step 1102 in FIG. If the fuel supply amount is Ti1, the fuel pressure lower limit is P1 from FIG.
[0038]
FIG. 13 is a routine for estimating the fuel pressure, and is executed for each reference. This corresponds to the fuel pressure estimation means D. Here, FIG. 18 shows the fuel pressure increase characteristic of the fuel pump corresponding to the crank angle, which is assumed to be known by experiments and the like.
In step 1301, the previous estimated fuel pressure value Pest is read. However, in the case of the first reference after the start, since the previous estimated value does not exist, the previous estimated fuel pressure value Pest is generated based on the crank angle at the time of start and a part of the characteristics of FIG.
[0039]
In step 1302, as shown in FIG. 20, the transition of the fuel pressure Ppump by the high-pressure fuel pump while the crank angle subsequently advances by 180 CA ° is used. The final value of the previous estimated fuel pressure value read in step 1301 is used as the initial value. Estimated from 18 characteristics. In the next step 1303, the fuel supply amount Ti1 obtained in the routine of FIG. 11 is read. In step 1304, the fuel supply amount Ti1 and the fuel pressure Ppump of the high-pressure fuel pump estimated by 1302 are used to supply the fuel from the relationship of FIG. The time Tpulse is calculated.
[0040]
In step 1305, the rate of decrease in fuel pressure when a pulse of the fuel supply time Tpulse is output is calculated from characteristics that have been examined in advance through experiments or the like. When the fuel injection pulse width is the same, when the fuel pressure is high, a lot of fuel is injected and the fuel pressure is greatly reduced, but when the fuel pressure is low, only a small amount of fuel is supplied, so the amount of decrease in fuel pressure is also small. The ratio between the fuel pressure and the fuel pressure decrease amount is considered to be the same in both cases. Therefore, it is possible to use a table as shown in FIG. 19 in which the fuel supply time Tpulse and the fuel pressure reduction rate are simply proportional.
[0041]
In step 1306, from the fuel pressure Ppump of the pump estimated in step 1302 (FIG. 20) and the fuel pressure value decrease ratio obtained in step 1305, the fuel pressure transition Pdown during fuel supply is estimated as shown in FIG. This routine ends.
FIG. 14 is a routine for determining the fuel supply start cylinder, and is executed for each reference. This corresponds to the fuel supply cylinder determination means E.
[0042]
In step 1401, the lowered fuel pressure value Pdown at the time of fuel supply estimated in the routine of FIG. 13 is read, and in step 1402, the fuel pressure lower limit value P1 calculated in the routine of FIG. 12 is read. In the next step 1403, the two are compared, and if the estimated fuel pressure value Pdown is equal to or greater than the fuel pressure lower limit value P1 (Pdown ≧ P1), the process proceeds to step 1404, and fuel is supplied as scheduled to the cylinder where the fuel supply timing comes. In step 1405, an injection pulse for the fuel supply time Tpulse is set. In step 1406, Pdown is substituted for Pest, and the process is terminated.
[0043]
On the other hand, if the estimated fuel pressure value Pdown is smaller than the fuel pressure lower limit value P1 in step 1403 (Pdown <P1), the process proceeds to step 1407, and then the fuel supply is stopped and the fuel supply is deferred. In step 1408, the estimated fuel pressure value Ppump when no fuel is supplied is substituted for Pest, and the process ends.
With the above processing, the engine can be reliably started according to the state at that time without causing deterioration of combustion or misfiring based on the fuel supply amount Ti1 at the time of starting and the rotational speed N. .
[0044]
The routines in FIGS. 11 to 14 are all reference jobs, but these routines are sequentially executed in ascending order in the figure. This control is executed from the start, and after the first fuel supply is performed, the execution ends after a predetermined time (for example, 5 s) or a predetermined combustion cycle (for example, 50 combustion cycles) has elapsed.
Next, a second embodiment is shown.
[0045]
In the first embodiment, there is no particular restriction when calculating the fuel pressure lower limit value P1 in step 1204 of FIG. However, the fuel pressure lower limit value is calculated to be very low when the fuel supply amount is small, or when the rotation speed is low and the fuel supply time can be long, which allows an extremely low fuel pressure, resulting in insufficient fuel atomization. there is a possibility.
In order to compensate for this, a lower limiter that limits the minimum value of the fuel pressure lower limit value may be provided to correct the calculated fuel pressure lower limit value. The value of the lower limiter may be a map value determined from the engine speed N and the fuel supply amount Ti as shown in FIG. 22, or may be a constant value regardless of the operating conditions as shown in FIG.
[0046]
In this case, the routine shown in FIG. 15 is used as the fuel pressure lower limit calculation means C instead of the routine shown in FIG. The routine shown in FIG. 15 is executed for each reference. After calculating the fuel pressure lower limit value P1 in steps 1501 to 1504 in the same manner as in the first embodiment, correction by the lower limiter is performed in step 1505. This corresponds to the fuel pressure lower limit correction means.
Thus, even when the fuel supply amount Ti is small or the rotational speed N is low, the fuel pressure lower limit value P1 does not become extremely low, and the fuel is sufficiently atomized, so that deterioration of combustion and misfire can be prevented.
[0047]
A third embodiment is shown.
In the first embodiment, when the estimated fuel pressure value Ppump in FIG. 20 is estimated, future estimation is performed based on the previous estimated value. However, the previous fuel pressure data uses the actually measured value by the fuel pressure sensor 10, When estimating the future fuel pressure, a correction factor may be calculated from the previous estimated value and the previous actual measured value to correct the fuel pressure increase characteristic in FIG. 18 and be used for future estimation. .
[0048]
In this case, as the fuel pressure estimating means D, the routine of FIG. 16 is used instead of the routine of FIG. 13 of the first embodiment. The routine of FIG. 16 is executed for each reference.
In step 1601, the fuel pressure sensor detected value Psen for the previous predetermined period (between references) as shown in FIG. 23 is read, and in the subsequent step 1602, the previously used fuel pressure estimated value Pest corresponding to the sensor detected value Psen is read. In step 1603, the correction coefficient α of the estimated fuel pressure value is calculated from the data read in steps 1601 and 1602. Specifically, the correction coefficient α is obtained by the following equation as the ratio of the average values.
[0049]
α = Ave (Psen) / Ave (Pest)
In step 1604, the fuel pressure Ppump by the high-pressure fuel pump is estimated from the characteristics of FIG. 18 as in the first embodiment. In step 1605, the estimated value Ppump is corrected by the following equation using the correction coefficient α calculated in step 1603. Get P'pump.
P'pump = Ppump x α
Thereafter, in each step from step 1606 to step 1609, the estimated value P′pump after correction is calculated in the same manner as in the procedure of FIG. 13 of the first embodiment, and the fuel pressure decreased when fuel is supplied. The value Pdown is estimated as shown in FIG. 23, and this routine is terminated.
[0050]
This makes it possible to estimate more accurately how the fuel pressure value changes when fuel is supplied.
In this embodiment, the ratio between the average value Ave (Pest) of the previous fuel pressure estimated value sequence and the average value Ave (Psen) of the sensor output sequence is used to calculate the correction coefficient α of the estimated fuel pressure value. This may be calculated only from data at a predetermined crank angle. Although only the previous combustion data is used here, the correction coefficient may be obtained using the past number of combustion data.
[0051]
The correction based on the sensor output may be performed not only on the fuel pump characteristic Ppump but also on the characteristic of the fuel pressure decrease rate with respect to the fuel supply time Tpulse (FIG. 19). In this case, the fuel pressure decrease rate when the fuel is supplied may be detected from the sensor output, and the correction value β may be set based on this data.
As in the first embodiment, this control is executed from the start and if a predetermined time (for example, (5 s) or a predetermined combustion cycle (for example, 50 combustion cycles) has elapsed after the initial fuel supply. , The execution shall be terminated.
[0052]
Also in this embodiment, as in the second embodiment, if a lower limiter is provided for the fuel pressure lower limit value P1, it is possible to more accurately determine whether to supply fuel or postpone fuel supply.
A fourth embodiment will be described.
In the first and second embodiments, when estimating the estimated fuel pressure value of FIG. 21, the fuel pump fuel pressure increase characteristic Ppump is the same in all operations (FIG. 18). However, if the engine is equipped with a fuel temperature sensor 19 that detects the temperature of the fuel (hereinafter referred to as the fuel temperature), the difference in fuel pressure increase characteristics due to subtle changes in the fuel properties based on the difference in fuel temperature is experimentally determined in advance. By examining this, it becomes possible to estimate the fuel pressure increase characteristic of the pump more accurately based on the fuel temperature at that time.
[0053]
In this case, as the fuel pressure estimation means D, the routine of FIG. 24 is used instead of the routine of FIG. 13, and the table of FIG. 25 is used instead of the table of FIG. The routine shown in FIG. 24 is executed for each reference. After reading the previous estimated fuel pressure value Pest in step 2401, the fuel temperature is read in step 2402, and in step 2403, based on the fuel temperature, the data shown in FIG. The estimated fuel pressure value Ppump of the high-pressure fuel pump is calculated. Thereafter, similarly to FIG. 13, the reduced fuel pressure value (Pdown) at the time of fuel supply is estimated by steps 2404 to 2407.
[0054]
Here, in the case of the configuration using the fuel pressure sensor 10 as shown in the third embodiment, the difference in the fuel pressure increase characteristic of the fuel pump due to the difference in the fuel temperature is also corrected based on the detected value of the fuel pressure sensor 10. 24 and 25 are not necessary.
In each of the embodiments described above, the engine 1 has four cylinders and the fuel pump discharges fuel four times per two rotations of the engine. However, the present invention is not limited to this, and the fuel discharge cycle of the fuel pump is as follows. If the characteristic of the fuel pressure with respect to the crank angle is known, it does not necessarily have the same cycle as the engine rotation.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of the present invention.
FIG. 2 is a system configuration diagram showing an engine portion of an embodiment of the present invention.
FIG. 3 is a system configuration diagram showing a circuit portion of an embodiment of the present invention.
FIG. 4 is a diagram showing the opening / closing timing of intake valves and exhaust valves.
FIG. 5 is a graph showing the relationship between fuel pressure and fuel supply time when the fuel supply amount is constant.
FIG. 6 is a diagram showing the fuel pressure increase process by the fuel pump.
FIG. 7 is a graph showing changes in fuel pressure and rotation speed when the amount of fuel supplied at start-up is small
FIG. 8 is a graph showing changes in fuel pressure and rotational speed when the amount of fuel supplied at start-up is large
FIG. 9 is a graph showing changes in fuel pressure and rotation speed when the method of the present invention is applied when the amount of fuel supplied at start-up is large.
FIG. 10 is a flowchart showing a procedure for detecting an operating state.
FIG. 11 is a flowchart showing a procedure for calculating a fuel supply amount.
FIG. 12 is a flowchart showing a procedure for calculating the lower limit value of the fuel pressure.
FIG. 13 is a flowchart showing a procedure for estimating fuel pressure.
FIG. 14 is a flowchart showing a procedure for determining whether or not to supply fuel.
FIG. 15 is a flowchart showing a second procedure for calculating the lower limit value of the fuel pressure.
FIG. 16 is a flowchart showing a second procedure for estimating fuel pressure.
FIG. 17 is a graph showing the relationship between the water temperature at the start and the fuel supply amount
FIG. 18 is a graph showing the characteristics of fuel pressure increase by the fuel pump with respect to the crank angle.
FIG. 19 is a graph showing the relationship between the fuel injection pulse width and the fuel pressure decrease width
FIG. 20 is a diagram showing how fuel pressure changes are estimated by a fuel pump.
FIG. 21 is a diagram showing a state of estimation of fuel pressure change in consideration of the influence of both fuel pressure change by a fuel pump and fuel pressure drop by fuel supply.
FIG. 22 is a diagram illustrating an example of a lower limiter map
FIG. 23 is a diagram showing a state of estimation of a fuel pressure change in consideration of the effects of both a fuel pressure change by a fuel pump and a fuel pressure drop by fuel supply when a fuel pressure sensor is provided.
FIG. 24 is a flowchart showing a third procedure for estimating fuel pressure.
FIG. 25 is a graph showing the fuel pressure increase characteristic of the fuel pump with respect to the crank angle when the fuel temperature is different.
[Explanation of symbols]
1 organization
2 Throttle valve
3 Surge tank
4 Intake manifold
5 Intake valve
6 Injector for direct injection
7 Combustion chamber
8 Spark plug
9 Air flow meter
10 Fuel pressure sensor
19 Fuel temperature sensor

Claims (14)

In a direct injection type internal combustion engine control device for injecting fuel directly into a cylinder at a high pressure by a direct injection injector,
An operating state detecting means for detecting the operating state of the engine;
Fuel supply amount calculating means for calculating the fuel supply amount at the time of engine start;
Fuel pressure lower limit value calculating means for calculating a lower limit value of the fuel pressure required at the start based on the detection result of the operating state detecting means and the calculation result of the fuel supply amount calculating means;
Fuel pressure estimation means for estimating a change in fuel pressure when fuel is supplied based on the detection result of the operating state detection means and the calculation result of the fuel supply amount calculation means;
Fuel supply start cylinder determining means for determining a cylinder to start fuel supply at the start based on the calculation result of the fuel pressure lower limit calculating means and the estimation result of the fuel pressure estimating means;
A control device for an in-cylinder direct injection internal combustion engine, comprising:   2. The control apparatus for a direct injection type internal combustion engine according to claim 1, wherein the fuel pressure estimation means estimates in advance a change in fuel pressure due to fuel supply before fuel supply. In a direct injection type internal combustion engine control device for injecting fuel directly into a cylinder at a high pressure by a direct injection injector,
An operating state detecting means for detecting the operating state of the engine;
Fuel supply amount calculating means for calculating the fuel supply amount at the time of engine start;
Fuel pressure lower limit value calculating means for calculating a lower limit value of the fuel pressure required at the start based on the detection result of the operating state detecting means and the calculation result of the fuel supply amount calculating means;
Fuel pressure estimation means for estimating a change in fuel pressure when fuel is supplied based on the detection result of the operating state detection means and the calculation result of the fuel supply amount calculation means;
Fuel supply start cylinder determining means for determining a cylinder to start fuel supply at the start based on the calculation result of the fuel pressure lower limit calculating means and the estimation result of the fuel pressure estimating means;
Comprising
The fuel pressure estimating means estimates a change in fuel pressure after fuel supply from a crank angle detected by the operating state detecting means, a fuel supply amount calculated by the fuel supply amount calculating means, and a predetermined fuel pump characteristic. A control device for a direct injection type internal combustion engine, characterized in that it is a thing.   4. The control apparatus for a direct injection type internal combustion engine according to claim 3, wherein the predetermined fuel pump characteristic is a fuel pressure increase characteristic of a fuel pump corresponding to a crank angle. The fuel pressure estimation means estimates the transition of the fuel pressure for each reference signal output by the crank angle sensor every 180 ° CA ,
The fuel pressure estimated based on the previous fuel pressure estimated value with the final value of the previous fuel pressure estimated value as the initial value, and the fuel pressure decrease amount calculated based on the fuel supply time calculated from the estimated fuel pressure and the fuel supply amount, 5. The control device for a direct injection type internal combustion engine according to claim 4 , wherein the transition of the fuel pressure is estimated from the above. First at the time of fuel pressure estimate after starting, the initial value, and the crank angle at the time of starting, the pre-stored cylinder direct injection type according to claim 5, characterized in that determined by the fuel pressure rise characteristics of the fuel pump Control device for internal combustion engine. The operating state detecting means detects a crank angle of the engine by a crank angle sensor installed in the internal combustion engine, and calculates the engine speed based on the crank angle sensor. The control apparatus for a direct injection type internal combustion engine according to any one of claims 6 to 9. The fuel supply amount calculation means, based on the coolant temperature of the engine, any one of claims 1 to 7, characterized in that to determine the fuel supply quantity at engine starting from a predetermined table The direct-injection direct-injection internal combustion engine control device according to claim 1. The fuel pressure lower limit calculating means includes a maximum fuel supply time calculated based on a crank angle section in which fuel can be supplied and an engine speed detected by the operating state detecting means, and the fuel supply amount calculating means. 2. The lower limit value of the fuel pressure necessary to finish supplying the fuel supply amount within the maximum time is calculated from the fuel supply amount calculated in step 1 from a predetermined table. The control device for a direct injection type internal combustion engine according to any one of claims 8 to 9 . The fuel pressure lower limit calculating means, according to claim 9, characterized in that it is configured to include a fuel pressure lower limit correction means a limiter for limiting the minimum value of the fuel pressure lower limit provided, to correct the lower limit value of the fuel pressure which the calculated A control apparatus for an in-cylinder direct injection internal combustion engine. While the internal combustion engine includes a fuel pressure sensor that detects fuel pressure, the fuel pressure estimation means includes a crank angle detected by the operating state detection means, a fuel supply amount calculated by the fuel supply amount calculation means, and a known fuel and characteristics of the pump, and an output of the fuel pressure sensor, a cylinder direct injection internal combustion engine according to any one of claims 1 to 10, characterized in that to estimate the change in the fuel pressure Control device. While the internal combustion engine includes a fuel temperature sensor that detects a fuel temperature, the fuel pressure estimation means includes a crank angle detected by the operating state detection means, a fuel supply amount calculated by the fuel supply amount calculation means, and a known and characteristics of the fuel pump, said from the output of the fuel temperature sensor, cylinder direct injection internal combustion according to any one of claims 1 to 10, characterized in that to estimate the change in the fuel pressure Engine control device. The fuel supply start cylinder determining unit compares the estimated value of the fuel pressure after the fuel supply calculated by the fuel pressure estimating unit with the fuel pressure lower limit value calculated by the fuel pressure lower limit value calculating unit, and calculates the fuel pressure. When the value is equal to or greater than the fuel pressure lower limit value, fuel is supplied to the cylinder at which the fuel supply timing has arrived. When the estimated fuel pressure value is smaller than the fuel pressure lower limit value, fuel supply is not performed and the next fuel is not supplied. 13. The control of a direct injection type internal combustion engine according to any one of claims 1 to 12 , wherein a cylinder for starting fuel supply is determined by performing similar processing at a supply timing. apparatus. 14. The control device for a direct injection type internal combustion engine according to any one of claims 1 to 13 , wherein the control is terminated when a predetermined period elapses after the engine is started.

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